<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        //1.先让客户输入年份
        let year = +prompt('请输入年份');

        //2.计算平年还是闰年

        if ((year % 400 == 0) || (year % 4 == 0 && year % 100 != 0)) {
            // 满足前面条件
            document.write((year + '是闰年'));
        } else {
            // 前面条件不达成
            document.write((year + '是平年'));
        };

        // document.write(year);
    </script>
</body>

</html>